The present invention describes a fragrance delivery system which releases fragrant aldehydes or ketones and/or fragrant compounds containing an olefin function upon exposure to light. This system comprises xcex1-keto esters of formula 
in which Rxe2x80x2* and Rxe2x80x3* have the meaning as defined in the application and which are generally, in case of Rxe2x80x2*, an alkyl group carrying an abstractable hydrogen in xcex3-position relative to the xcex1-keto function and carrying a moiety from which is derived a fragrant compound containing an olefin function, and, in case of Rxe2x80x3*, the organic part of a primary or secondary alcohol from Rxe2x80x3*OH which is derived a fragrant aldehyde or ketone.
The present invention relates to the field of perfumery. It relates, more particularly, to xcex1-keto esters, as defined below, of alcohols which are precursors of fragrant aldehydes and ketones and which are capable of releasing said fragrant ketone or aldehyde upon exposure to light, more particularly daylight. Said xcex1-keto esters may furthermore contain, in xcex1-position to the keto group, an alkyl group which may contain various substituents and which alkyl group is derived from a fragrant molecule possessing an olefinic unsaturation. The unsaturated molecule and/or the aldehyde or ketone are released upon exposure to light, in particular daylight, of the xcex1-keto ester.
There exists, in perfumery, a particular interest in compounds which are capable of xe2x80x9cfixingxe2x80x9d fragrant molecules, for example by chemical bonding or intramolecular forces like absorption, and releasing said fragrant molecules over a prolonged period of time, for example by the action of heat, enzymes, or even sunlight. Fragrant molecules have to be volatile in order to be perceived. Although many fragrant compounds are known which show a good substantivity, i.e. they will remain on a surface to which they have been applied for several days and can hence be perceived over such a period of time, a great number of fragrant compounds are very volatile, and their characteristic smell can no longer be perceived several hours after their application.
It is thus desirable to dispose of fragrance delivery systems which are capable of releasing the fragrant compound or compounds in a controlled manner, maintaining a desired smell over a prolonged period of time.
We have now developed a fragrance delivery system which is capable of releasing fragrant aldehydes or ketones and/or fragrant compounds containing an olefin function upon exposure to light, and in particular daylight.
The object of the present invention is a fragrance delivery system comprising xcex1-keto esters of formula 
in which
Rxe2x80x2* is hydrogen or a linear or branched, unsubstituted or substituted alkyl group or alkylene group from C1 to C35, an unsubstituted or substituted cycloalkyl group from C3 to C8, an unsubstituted or substituted phenyl group, wherein said alkyl, alkylene, cycloalkyl and phenyl groups may comprise one or several hetero atoms not directly linked to the xcex1-keto group and selected from the group consisting of oxygen, nitrogen, phosphorous and sulfur, or
Rxe2x80x2* is a substituted or unsubstituted, linear or branched alkyl group carrying an abstractable hydrogen in xcex3-position relative to the xcex1-keto function and comprising a moiety from which is derived a fragrant compound containing an olefin function, such that said fragrant compound containing an olefin function is eliminated after abstraction of said xcex3-hydrogen atom;
Rxe2x80x3* is hydrogen or a methyl, ethyl or tert-butyl group or is the organic part of a primary or secondary alcohol from which is derived a fragrant aldehyde or ketone, and at least one of the groups Rxe2x80x2* and Rxe2x80x3* being a group which is derived from a fragrant compound.
Many of the xcex1-keto ester compounds of the above formula are new. Certain compounds are not, however, such as those of the above formula when Rxe2x80x2* is a methyl group, or when Rxe2x80x3* is a menthyl or a benzyl group. Specifically, (xe2x88x92)-(1S,1R)-1,7,7- trimethylbicyclo[2.2.1]heptan-2-yl (4-methylphenyl)oxoacetate and hexyl(cyclohexyl)oxoacetate are excluded.
In the above definition, when reference is made to a fragrant compound, aldehyde or ketone, it is always meant a compound which not only has an odor, but which is also known to a person skilled in the art as being useful as a perfuming ingredient for the formulation of perfumes or perfumed articles. The criteria a useful perfuming ingredient has to fulfil are known to a person skilled in the art and include, amongst others, a certain originality of the odoriferous note, stability and a certain price/performance ratio. Non-limiting examples for fragrant compounds which can be used with the xcex1-keto esters of the invention will be mentioned below.
The xcex1-keto esters of the above formula (I) release fragrant compounds upon exposure to light, in particular daylight. The xcex1-keto esters of formula (I), however, are also capable of releasing a fragrant compound containing an olefin function from the group Rxe2x80x2* in 1-position relative to the keto function, or a fragrant aldehyde or ketone which is derived from the alcohol Rxe2x80x3*OH from which the organic part Rxe2x80x3* is present in the ester function of the keto esters of the present invention, or even both.
From the above, it is clear that when reference is made to the organic part Rxe2x80x3* of a fragrant alcohol Rxe2x80x3*OH, Rxe2x80x3* is the hydrocarbyl rest of said alcohol, e.g. a menthyl radical in case Rxe2x80x3*OH is menthol.
The release of the fragrant compound from the keto esters occurs in an elimination reaction after an intramolecular transfer of an abstractable hydrogen radical, in xcex3-position to the xcex1-keto function, to said keto function. The respective part of the molecule from which the hydrogen radical has been abstracted is subsequently released from the reduced keto ester, with concomitant formation of a double bond. The above is illustrated in the scheme below in which possible substituents in the respective parts of the molecules have been omitted for reasons of clarity. The double bonds which will be formed after elimination are indicated by dotted lines. 
It is to be understood that the xcex1-keto esters of the present invention can release only one or both molecules of fragrant compound per molecule of xcex1-keto ester. When the hydrogen transfer to the xcex1-keto function is able to occur from the one or the other side of said function, as illustrated above, a certain part of the molecules will release a ketone or aldehyde and a certain part will release the olefin compound. The proportions of the two products released depend on the relative rate of each hydrogen transfer reaction. According to the effect desired, the xcex1-keto esters of the invention can be tailored to release exclusively a fragrant ketone or aldehyde, or exclusively a fragrant compound containing an olefin group, or both. When only one of the two classes of fragrant compounds is to be released from the xcex1-keto esters of the invention, the part of the molecule from which no release shall occur does not contain an abstractable hydrogen atom in xcex3-position to the keto function, i.e. either no hydrogen atom at all is present in the said position, or it is one which is not abstracted.
It is also clear that the xcex1-keto esters according to the invention can, in a first step, release the olefin compound under formation of a molecule which does not any longer contain an abstractable hydrogen atom in xcex3-position to the keto function (left side of the molecule as designed above) ; in a second step, this molecule can then release the ketone or aldehyde from the ester function.
A fragrance delivery system which contains the xcex1-keto esters of the above formula (I) has the advantages that the release of the fragrant compound occurs in a more or less constant amount. No initial burst of very intensive odor which becomes imperceptible after a relatively short period of time occurs, as is often observed with volatile aldehydes or ketones or fragrant compounds containing an olefin group. With the xcex1-keto esters of the present invention, such disadvantages are obviated because the esters will remain on a surface to which they have been applied or in the solution into which they have been incorporated. Upon exposure to light, the fragrant compound or compounds are released, and this reaction can provide perceptible amounts of the compound over days or weeks, depending, amongst others, on the amount or the concentration of the xcex1-keto esters, the time of exposure to light and its intensity.
A further advantage of the a-keto esters according to formula (I) is the protection of the reactive, unstable aldehyde or keto function in the molecules to be released against degradation which may occur during storage.
Additionally, the xcex1-keto esters of the present invention allow for the generation of mixtures of two different fragrant compounds, and in different proportions, if desired.
In principle, any fragrant aldehyde or ketone which is known in the art can be released from the xcex1-keto esters of the invention in which they are chemically bound in the form of the ester of their corresponding secondary or primary alcohol.
Non-limiting examples for fragrant aldehydes which can be released from the xcex1-keto esters include saturated and unsaturated linear and branched aldehydes from C6 to C13, citral, citronellal, campholenic aldehyde, cinnamic aldehyde, hexylcinnamic aldehyde, formyl pinane, hydroxycitronellal, cuminic aldehyde, vanillin, ethylvanillin, Lilial(copyright)[3-(4-tert-butylphenyl)-2-methylpropanal; origin: Givaudan-Roure SA, Vernier, Switzerland], Lyral(copyright) [4- and 3-(4-hydroxy-4-methylpentyl)-3-cyclohexene-1-carbaldehyde; origin: International Flavors and Fragrances, USA], Bourgeonal(copyright) [3-(4-tert-butylphenyl)propanal; origin: Quest International, Naarden, Netherlands], heliopropanal [3-(1,3-benzodioxol-5-yl)-2-methylpropanal; origin: Firmenich SA, Geneva, Switzerland], Zestover (2,4-dimethyl-3-cyclohexene-1-carbaldehyde; origin: Firmenich SA, Geneva, Switzerland), Trifernal(copyright) (3-phenylbutanal ; origin: Firmenich SA, Geneva, Switzerland), xcex1-sinensal, (4-methylphenoxy)acetaldehyde, 1,3-benzodioxol-5-carboxaldehyde (heliotropine), Scentenal(copyright) [8(9)-methoxy-tricyclo[5.2.1.0.(2,6)]decane-3-(4)-carbaldehyde; origin: Firmenich SA, Geneva, Switzerland], Liminal(copyright) [(4R)-1-p-menthene-9-carbaldehyde; origin: Firmenich SA, Geneva, Switzerland], Cyclosal [3-(4-isopropylphenyl)-2-methylpropanal; origin: Firmenich SA, Geneva, Switzerland], ortho- and para-anisaldehyde, 3-methyl-5-phenylpentanal, Acropal(copyright) [4-(4-methyl-3-pentenyl)-3-cyclohexene-1-carbaldehyde; origin: Givaudan-Roure SA., Vernier, Switzerland], Intreleven(copyright) aldehyde (mixture of 10-undecenal and 9-undecenal; origin: International Flavors and Fragrances, USA), muguet aldehyde [(3,7-dimethyl-6-octenyl)acetaldehyde; origin: International Flavors and Fragrances, USA], 2,6-dimethyl-5-heptanal, Precyclemone(copyright) B [1-methyl-4-(4-methyl-3-pentenyl)-3-cyclohexen-1-carbaldehyde; origin: International Flavors and Fragrances, USA] and Isocyclocitral(copyright) (2,4,6-trimethyl-3-cyclohexene-1-carbaldehyde; origin: International Flavors and Fragrances, USA).
Non-limiting examples for ketones which can be released from the xcex1-keto esters include camphor, carvone, menthone, ionones, irones, damascenones and damacones, benzyl acetone (4-phenyl-2-butanone), 1-carvone, 4-(4-hydroxy-1-phenyl)-2-butanone (raspberry ketone), Hedione(copyright) (methyl dihydrojasmonate; origin: Firmenich SA, Geneva, Switzerland), Neobutenone [1-(5,5-dimethyl-1-cyclohexen-1-yl)-4-penten-1-one; origin: Firmenich SA, Geneva, Switzerland], Calone(copyright) (7-methyl-2H,4H-1,5-benzodioxepin-3-one; origin: C.A.L. SA, Grasse, France), Sulfox [(1R,4R)-8-mercapto-3-p-menthanone; origin: Firmenich SA, Geneva, Switzerland], Orivone(copyright) [4-(1,1-dimethylpropyl)-1-cyclohexanone; origin: International Flavors and Fragrances, USA], Delphone (2-pentyl-1-cyclopentanone; origin: Firmenich SA, Geneva, Switzerland), 2-naphthalenyl-1-ethanone, Veloutone (2,2,5-trimethyl-5-pentyl-1-cyclopentanone; origin: Firmenich SA, Geneva, Switzerland), 4-isopropyl-2-cyclohexen-1-one, Iso E Super(copyright) [isomer mixture of 1-(octahydro-2,3,8,8-tetrame-2-naphthalenyl)-1-ethanone; origin: International Flavors and Fragrances, USA], Plicatone [5-methyl-exo-tricyclo[6.2.1.0(2,7)]undecan-4-one; origin: Firmenich SA, Geneva, Switzerland] ; and macrocyclic ketones such as, for example Exaltone(copyright) (cyclopentadecanone), Delta Muscenone (mixture of 3-methyl-4-cyclopentadecen-1-one and 3-methyl-5-cyclopentadecen-1-one) and Muscone (3-methyl-1-cyclopentadecanone), all from Firmenich SA, Geneva, Switzerland.
With respect to the fragrant compounds carrying an olefin group, in principle any compound containing such olefin group and, in addition, any osmophoric group known in perfumery can be used. As non-limiting examples for osmophoric groups, one can cite alcohol, ether, ester, aldehyde and keto groups, the thio analogues of the said groups, nitrile, nitro and olefin groups.
As non-limiting examples for fragrant compounds which carry an olefin group, there can be cited linalool, 1,3,5-undecatrienes, myrcene, myrcenol, dihydromyrcenol, nerolidol, sinensals, limonene, carvone, farnesenes, isopentyrate (1,3-dimethyl-3-butenyl isobutyrate; origin: Firmenich SA, Geneva, Switzerland), allyl 3-methylbutoxyacetate, eugenol, Rosalva (9-decen-1-ol; origin: International Flavors and Fragrances, USA), and allyl heptanoate.
It is quite obvious, however, that the invention is perfectly general and can relate to many other aldehydes, ketones and olefins which are useful as fragrant compounds. The person skilled in the art is quite able to choose these compounds from the general knowledge in the art and from the olfactive effect it is desired to achieve. The above list is therefore more illustrative for the compounds which are known to a person skilled in the art, and whose delivery can be improved. It is clearly quite impossible to cite in an exhaustive manner all aldehydes, ketones and olefins which have a pleasant odor and which can be used in the form of derivatives in the xcex1-keto esters of formula (I) from which they are released upon exposure to light.
The xcex1-keto esters of the present invention are in particular appropriate for delivering fragrant aldehydes, ketones and fragrant compounds containing an olefin group which are very volatile or which have a low perception threshold. Preferred aldehydes and ketones include citronellal, citral, hydroxycitronellal, Hedione(copyright), Lilial(copyright), raspberry ketone, anisaldehyde, menthone, Delphone, Orivone(copyright), 2-naphthalenyl-1-ethanone, and aldehydes from C6 to C13, saturated or unsaturated linear or branched. Preferred fragrant compounds containing an olefin group include linalool, myrcene, myrcenol and Rosalva(copyright).
In case the xcex1-keto esters of the present invention are used to release exclusively aldehydes or ketones, the group Rxe2x80x2* is hydrogen, phenyl, cyclohexyl or cyclopentyl, methyl, ethyl, n-propyl, isopropyl, sec-butyl, isobutyl or tert-butyl, i.e. groups which do not provide an abstractable hydrogen atom in xcex3-position to the xcex1-keto function or which do not form a stable radical when a hydrogen radical is abstracted from them. In the latter case, small amounts of olefin may be formed which however do not interfere with the aldehyde or ketone released.
Likewise, when the xcex1-keto esters of the present invention are used to release a fragrant compound containing an olefin group only, then the group Rxe2x80x3* will be hydrogen or a methyl, ethyl or tert-butyl group, thus a group which does not provide an abstractable proton in xcex3-position to the xcex1-keto function or which do not form a stable radical when a hydrogen radical is abstracted from them.
It is preferred when the fragrance delivery system of the present invention contains xcex1-keto esters of formula (I) in which Rxe2x80x3* is the organic part of a primary or secondary alcohol from which is derived a fragrant aldehyde or ketone and in which Rxe2x80x2* is a phenyl, cyclohexyl or cyclopentyl group or a linear or branched alkyl group from C1 to C4, with the exception of an n-butyl group.
A fragrance delivery system containing the xcex1-keto esters of formula (I) may comprise a solvent the choice of which is not supposed to be critical. Suitable classes of solvents include alcohols, ethers, esters, ketones, amines and aminoalcohols.
Depending on the general application conditions or on the product into which the xcex1-keto esters according to the present invention are incorporated, one can sometimes also observe the release of alcohols Rxe2x80x3*OH, due to saponification of the ester function, or due to reduction of the aldehyde or ketone formed by irradiation.
The xcex1-keto esters of formula (I) can be prepared, on the one hand, by esteriication of the respective xcex1-ketoacids with the primary or secondary alcohols which are the precursors of the fragrant aldehydes and ketones to be releasead. Another way for the preparation of the xcex1-keto esters of the present invention is the reaction of the bis(oxalyl) ester of the primary or secondary precursor alcohol Rxe2x80x3*OH with the Grignard compound of the appropriate group Rxe2x80x2* as defined in formula (I). The reaction is illustrated in the scheme I below. 
The bis(oxalyl) ester is prepared from oxalyl chloride and the desired alcohol, see Synth. Commun. 1981, (11), 943-946 and Org. Synth. Coll. Vol. II 1943, 425-427.
Another synthetic route leading to the desired xcex1-keto esters of formula (I) is the Grignard reaction of the readily available bis(oxalyl)esters of lower aliphatic alcohols such as, for example, methanol, ethanol or propanol, with the Grignard compound of the respective group Rxe2x80x2*, resulting in the intermediate ester (II). This said ester (II) is then submitted to a transesterification reaction with the respective precursor alcohol Rxe2x80x3*OH, to give the desired xcex1-keto ester. This reaction is outlined in the following scheme II in which Rxe2x80x2* and Rxe2x80x3* have the meaning defined in formula (I). Hal is Cl, Br or I and R is a lower alkyl group such as, for example, methyl, ethyl, propyl or butyl. 
Various xcex1-keto esters of formula (I) in which Rxe2x80x2* is hydrogen or a phenyl or methyl group and Rxe2x80x3* is derived from the alcohol precursor of a fragrant aldehyde are described in the literature.
Also known is hexyl (cyclohexyl)oxoacetate (see DE-OS 29 09 951 to Bayer AG, describing the use of the said compound as starting product for the synthesis of catalysts for the polymerisation of olefins), which would release n-hexanal upon irradiation.
In Biochem. Z. 1935, (277), p 426-436, there is described the synthesis of the (xe2x88x92)-bornyl ester of (4-methylphenyl)oxoacetic acid, i.e. (xe2x88x92) (1S,2R), 1,7,7-trimethylbicyclo[2.2.1]heptan-2-yl (4-methylphenyl)oxoacetate. The compound is characterized by its physical data.
There are furthermore known, from the chemical literature, various compounds according to the above formula (I) wherein ORxe2x80x3* is a menthyl or a benzyl group, with the groups Rxe2x80x2* being various alkyl, alkenyl, cycloalkyl or phenyl groups as defined above.
There is nowhere found, however, any description or hint concerning the value of the compounds according to formula (I) in perfumery as a photosensitive molecule which will release a fragrant compound upon irradiation.
In the book of S. Arctander, Perfume and Flavors Chemicals, 1969, Montclair, N.J., USA, there are mentioned decyl 2-oxopropanoate, (Z)-3-hexenyl 2-oxopropanoate and 2-ethyl-3-methylbutyl 2-oxopropanoate, with a short description of their odor and their synthesis. It is not mentioned that the said molecules release fragrant compounds upon irradiation.
The release of the above-mentioned fragrant compounds from the delivery system occurs upon the exposure to light, e.g. the normal daylight which can penetrate through ordinary windows in houses and which is not particularly rich in UV-radiation. It goes without saying that upon exposure to bright sunlight, in particular outdoors, the release of the fragrant alcohol, aldehyde, ketone or alkene will occur faster and to a greater extent than upon exposure to the light in a room inside a building. Of course, the reaction which releases the fragrant compound from the delivery system can also be initiated by an appropriate artificial lamp.
The invention is also directed to a method of improving, enhancing or modifying odoriferous properties of a perfuming composition or a perfumed article comprising adding to the composition or article an effective amount of an xcex1-keto ester as described above, provided that decyl 2-oxopropanoate, (Z)-3-hexynyl 2-oxopropanoate and 2-ethyl-3-methylbutyl 2-oxopropanoate are excluded.
The fragrance delivery systems of the present invention can be used in any application in which a prolonged, defined release of the above-mentioned fragrant compounds is desired. They therefore mostly find use in functional perfumery, in articles which are exposed to daylight when in use or which are applied to other articles which thereafter are exposed to daylight. Suitable examples include air-fresheners in liquid and solid form which, with the delivery system of the present invention, still can release a fragrance when conventional air-fresheners, i.e. those not containing the system of the present invention, are exhausted. Other examples are various cleaners for the cleaning of surfaces of all kinds, e.g. window and household cleaners, all purpose-cleaners and furniture polish. The surfaces which have been cleaned with such cleaners will diffuse the smell of the perfume much longer than when cleaned with conventional cleaners. Other representative examples include detergents for fabric wash, fabric conditioners and fabric softeners which can also contain the delivery system of the present invention and which products can be in the form of powders, liquids or tablets. The fabrics and clothes washed or treated with such detergents or softeners will diffuse the fragrant compound even after having been stored for weeks or even months, in a dark place, like a wardrobe.
The release of the fragrant compound occurs in all the above-mentioned application examples. All possible types of window, household, all-purpose cleaners, air-fresheners, detergent, fabric wash and fabric softeners can be used with the fragrance delivery system of the present invention, which has revealed itself to be useful in all types of these above-mentioned application examples.
In the field of body care, the delivery systems according to the present invention have shown themselves to be particularly appropriate for an application in the hair care area, and specific examples include shampoos, hair conditioners, in particular leave-in conditioners, hairspray and other hair care products.
It can be said that generally all products which can be applied to a surface which is exposable to light may contain the system of the present invention. Examples include surfaces which belong to the human body, like skin or hair, surfaces in buildings and apartments, like floors, windows, tiles or furniture, or surfaces of fabrics, e.g. clothes. It is clear that the system of the invention can also be used to release fragrances from liquids, like in liquid air-fresheners. The possible applications of this type, however, appear to be less general than the application on the various surfaces mentioned wherein the ester of the invention will be deposed as a film on the respective surface.
Of course, the above examples are only illustrative and non-limiting as referring to preferred embodiments. All other current articles in functional and fine perfumery may contain the system of the present invention, and these articles include soaps, bath or shower gels, cosmetic preparations, body deodorants, and even perfumes or colognes.
In the above-cited applications, the device of the present invention can be used alone or with other perfuming ingredients, solvents and adjuvants of current use in the art. The nature and variety of these co-ingredients does not require a detailed description which, moreover could not be exhaustive, and a person skilled in the art will be able to choose said coingredients by his general knowledge and in function of the nature of the product to be perfumed and the olfactive effect sought. These perfuming ingredients belong to such varied chemical classes as alcohols, aldehydes, ketones, esters, ethers, acetates, nitrites, terpene hydrocarbons, nitrogen- or sulfur- containing heterocyclic compounds, as well as essential oils of natural or synthetic origin. By way of example, embodiments of compounds can be found in standard reference works, such as the book of S. Arctander, Perfume and Flavor Chemicals, 1969, Montclair, N,J., USA, or more recent versions thereof, or in other works of similar nature.
The proportions in which the system of the present invention can be incorporated in the various above-mentioned products vary within a wide range of values. These values depend on the nature of the fragrant compound to be released, the nature of the article or product which is to be perfumed and the desired olfactive effect, as well as on the nature of the co-ingredients in a given composition when the system of the present invention is used in admixture with perfuming co-ingredients, solvents or adjuvants of current use in the art.
By way of example, one can cite typical concentrations of the order of 0.01 to 5%, or even 10% by weight relative to the weight of the consumer products cited above into which it is incorporated. Higher concentrations than those mentioned above can be used when the system is applied in perfuming compositions, perfumes or colognes.
The invention will now be described in greater detail in the following examples in which the temperatures are indicated in degrees centigrade and the abbreviations have the usual meaning in the art.
General
The following chemicals were obtained from commercial sources: geraniol, magnesium turnings, 1,2-dichloroethane, 1,2-dibromoethane, 2-norbornyl bromide, bromocyclopentane, citronellol, decanol, 4-methoxybenzyl alcohol, Lilial(copyright), (xe2x88x92)-menthol, 2-pentylcyclopentanol, 4-(1,1-dimethylpropyl)- 1-cyclohexanol, 1-(2-naphthalenyl)ethanol, oxalyl chloride, diethyl oxalate, 3-methyl-2-oxo-pentanoic acid, 2-oxopropionic acid, 2-oxobutanoic acid, bromocyclohexane, bromobenzene, 2-oxopentanoic acid, 4-bromo acetophenone, ethylene glycol, 2-bromo-tetradecane, 1-bromotetradecane.
Execution of photorelease assays and analysis for xcex1-keto esters
Photorelease Assays
Photorelease assays were conducted on solutions or on films of the respective ester and will be described below in each of the examples referring to the respective mode of irradiation.
All samples were irradiated using a xenon lamp (Heraeus Suntest CPS at 460W/m2), a UV lamp (UVP Model UVL-28, 8W at 360 nm) or exposed to outdoor sunlight, as will be indicated for each sample in the respective examples.
Analysis
The mode of analysis for each sample which had been irradiated will be indicated in each respective example.
Analytical HPLC was carried out on a Spectra Physics instrument composed from a SP 8800 ternary pump, a SP 5750 injection valve, a SP 8780 autosampler, a Waters 490E UV detector and a Spectra Physics ChromJet integratorMacherey-Nagel Nucleosil 5 C18 reversed phase column (125 xc3x974 mm i.d.) eluted with a gradient from acetonitrile/water 1:1 to pure acetonitrile during 20 min. The injection volume was 50 xcexcl and the UV detector wavelength fixed at 220 nm.
Analytical GC for analysis of all-purpose/window cleaner applications: the on-column injections were carried out on a Carlo Erba MFC 500 using a precolumn (30 cm) and a Suppelco SPB-1 capillary column (30 m) at 115xc2x0 C. for 8 min, then to 280xc2x0 C., helium pressure 75 kPa, injection volume 2 xcexcl. All other GC analyses were carried out on the same instrument equiped with a Fisons AS 800 autosampler using a JandW Scientific DB1 capillary column (15 m) at 70 or 80xc2x0 C. for 10 min, then to 260xc2x0 C., helium pressure 50 kPa, injection volume 0.5 xcexcl.
Analytical GC for dynamic headspace analysis: Tenax cartridges were thermally desorbed in a PE ATD400 or a TDAS 5000 desorber. The volatiles were then analysed either with a Carlo Erba HRGC 5300 gas chromatograph coupled to Finnigan ITD-800 mass spectrometers using a Supelco SPB-1 capillary column (60 m, 0.75 mm i.d., film 1 micron) at 60xc2x0 C. for 5 min then to 120xc2x0 C. (3xc2x0 C./min) and 280xc2x0 C. (5xc2x0 C./min) for the citronellal analysis, and at 100xc2x0 C. then to 250xc2x0 C. (5xc2x0 C./min) for the menthone quantification or, alternatively, with a Carlo Erba Vega 6000 gas chromatograph using a Supelco SPB-1 capillary column (30 m, 0.53 mm i.d., film 1.5 micron) from 110xc2x0 C. to 200xc2x0 C. (6xc2x0 C./min) using He as carrier gas in both cases.